A number of power tools have been produced to facilitate forming a work piece into a desired shape. One such power tool is a miter table saw. Miter table saws present a safety concern because the saw blade of the miter table saw is typically very sharp and moving at a high rate of speed. Accordingly, severe injury such as severed digits and deep lacerations can occur almost instantaneously. A number of different safety systems have been developed for miter table saws in response to the dangers inherent in an exposed blade moving at high speed. One such safety system is a blade guard. Blade guards movably enclose the saw blade, thereby providing a physical barrier that must be moved before the rotating blade is exposed. While blade guards are effective to prevent some injuries, a user's finger is nonetheless in proximity to the moving blade, particularly when attempting to secure a work piece as the miter table saw is used to shape the work piece.
Accordingly, detection or sensing systems have been developed for use with various kinds of manufacturing equipment and power tools. Such detection systems are operable to trigger a reaction device by detecting or sensing the proximity or contact of some appendage of an operator with some part of the equipment. For example, existing capacitive contact sensing systems in table saws detect contact between the operator and the blade.
In particular, miter table saw safety systems have been developed which are intended to stop the blade when a user's hand approaches or touches the blade. Various stopping devices have been developed including braking devices which are physically inserted into the teeth of the blade. In general, upon detection of a person in the vicinity of the blade, a signal is processed and sent to a brake mechanism to stop blade rotation within a short period of time. One such system is disclosed in U.S. Pat. No. 8,943,937, the disclosure of which is incorporated herein by reference in its entirety. Another such system is disclosed in U.S. Pat. No. 9,387,598, the disclosure of which is incorporated herein by reference in its entirety. In other systems, a mechanical or electrical brake is used.
In many of these safety systems, electrical energy is provided to a drive member, which drives the rotational movement of the blade, and electrical energy is also provided to the blade, to generate a signal indicative of contact between the person and the blade. Thus, it is necessary to isolate the electrical energy provided to the drive member and the electrical energy provided to the blade. However, it is difficult to combine mechanical strength, to transfer rotation and torque from the drive member to the blade, with dielectric properties, to electrically isolate the electrical energy provided to the drive member from the electrical energy provided to the blade.
What is needed therefore is a connection between a drive member and a working element, such as a blade, which is able to transfer rotation and torque from the drive member to the working element and is also able to electrically isolate electrical energy provided to the drive member from electrical energy provided to the working element.